module _56

open System.Numerics

let exponentialDigitSum =
    let powDigitSum (a, b) =
        BigInteger.Pow(a,b)
        |> common.numDigits
        |> Seq.sum

    let third (_, _, c) = c

    common.crossMap (fun a b -> (a,b)) [2I..100I] [2..10]
    |> Seq.map (fun (a,b) -> (a,b,powDigitSum (a,b)))
    |> Seq.maxBy third